Angioedema

Angioedema is swelling that is similar to hives, but the swelling is under the skin instead of on the surface.

Hives are often called welts. They are a surface swelling. It is possible to have angioedema without hives.

Causes

Angioedema may be caused by an allergic reaction. During the reaction, histamine and other chemicals are released into the bloodstream. The body releases histamine when the immune system detects a foreign substance called an allergen.

Exams and Tests

The health care provider will look at your skin and ask if you have been exposed to any irritating substances. If your throat is affected, a physical exam might reveal abnormal sounds (stridor) when you breathe in.